It was a nasty surprise to unionists, who had not been consulted and were furious that the Republic of Ireland was given an advisory role in running Northern Ireland.

The AIA led to years of protests by unionists, who boycotted NIO ministers. The Ulster Unionists and DUP did not stand against each other in key elections until the 1990s.

On the date of the huge unionist protest outside City Hall on Saturday November 23 (when Ian Paisley famously bellowed ‘Never, never, never, never’) I was supposed to be at school (unusually, and embarrassingly for a boy of age 13, as I then was, our school had Saturday classes in the morning and games in the afternoon).

Given my interest in politics I bunked off the games, disguised my uniform as much as possible and got a bus from east Belfast into the rally.

Ben Lowry News Letter deputy editor

My hostile response to the AIA then was instinctive and crude and unformed by either family or school (almost no-one I knew was at the rally, and no-one from school, although I do recall an older boy played by the rules, unlike me, and asked permission to go – I don’t know if it was granted but recall his housemaster saying he disagreed with the rally).

Now, when I look back on the AIA after more than 30 years of following local politics, some things seem clear.

To anyone who feels strongly British, it was an outrage for Dublin to be given a formal role in Northern Ireland.

You do not have to be a fire-breathing loyalist to believe that this was a constitutional no-no, in the same way that Paris would not get a formal say in running Belgium merely because over 40 per cent of the country is French-speaking.

But specifically it was unforgivable for Dublin to get such a say given its lamentable failures against terrorism. Many isolated border Protestants (whose bravery I have come to admire, as someone who grew up in safe north Down) died because sectarian killers were allowed to roam those areas.

Insofar as they were ever caught by the ineffective garda and Irish Army, the southern authorities mostly refused to extradite them.

I don’t believe the unionist conspiracy theory that this was part of an organised republican plot that included the Irish government.

The latter mostly loathed the Provisionals. Unionists are falling into the same trap as nationalists who believe that London was involved in loyalist ‘death squads’ – patent rubbish. If London had wanted to get tough with republicans, they easily could have killed hundreds, even thousands, of them and this obviously never even came close to happening.

The Republic’s 1970s and 80s security failings were, first, incompetence and, second, ambivalence about the IRA. Yes, they loathed them but they loathed unionists too.

The problem for unionists was (and to a lesser extent still is) this. They were not much liked in London either. However, they seemed not to realise this, partly because Margaret Thatcher was prime minister, as emphatic a unionist as has inhabited Downing Street.

But Mrs Thatcher surrounded herself by very bright, very establishment and moderate men such as Geoffrey Howe and Douglas Hurd and in many issues this constrained her radicalism.

The unionist MPs of the 1950s and 60s were part of the Tory establishment but the Troubles brought in a more militant generation of unionist MPs in the DUP and sometimes UUP.

James Molyneaux, leader of the latter, was hardly militant but he was unbending. If he ever had the inclination to challenge Dr Paisley in any significant way (and it is far from clear that he did), then he lacked the confidence to do so.

As the years rolled by after the failure of Sunningdale, Molyneaux was sidelined, perhaps without knowing it because he was at home around Tory MPs, and was respected as a mild-mannered war veteran.

The 1984 Brighton bomb must have accelerated the Conservative establishment feeling that there needed to be some sort of deal, and they realised that Molyneaux was not a man to be part of it.

That Garrett FitzGerald was Taoiseach, not Charlie Haughey, made it easier for Mrs Thatcher. Crucially, she believed that Dublin would greatly improve its security response to the IRA, but this did not happen and she is said later to have regretted the deal.

Unionists can feel justifiably bitter that their stubbornness was punished, while John Hume’s boycott of the 1982 to 86 Assembly was rewarded. But then unionists have long been more overt in their intransigence than nationalists. Indeed they have been recklessly indifferent to PR.

The AIA had far-reaching consequences. Sam Butler, former editor of this newspaper, has written about how his attempts to promote liberal unionism were shattered by the deal. Moderates were not only sidelined by the gulf of unionist anger, they shared it. To understand that, read the full quote of Ian Paisley’s ‘never’ speech at the rally:

“Where do the terrorists operate from? From the Irish Republic! That’s where they come from! Where do the terrorists return to for sanctuary? To the Irish Republic!

“And yet Mrs Thatcher tells us that that Republic must have some say in our Province. We say never, never, never, never!”

Even many moderates, enraged by IRA violence, would have cheered that sentiment about Dublin getting a say after its security inaction.

But people in Great Britain remember the ‘never’ bit and it confirmed a sense, even among liberal Tories, of primitive and obdurate unionists.

Moderate unionists too came to loathe anti-AIA tactics, which flirted with paramilitarism and included attacks on the police. The 418,000 votes for anti-agreement candidates in the January 1986 Westminster protest by-elections was not repeated and those numbers never had the influence they might have done.

The agreement stuck yet it was 10 years before the UUP was taken over by David Trimble, a hard but flexible man who knew that if he didn’t strike a deal, worse than the AIA would one day follow.